Final follow-up on all University of Chicago breast cancer patients to obtain disease status, death dates where applicable, and documented cause of death. Initial correlation analyses of various disease parameters which show statistically significant relationships to estrogen receptor content or type of receptor present. More detailed multivariate analyses of patient data with particular reference to receptor assays. These analyses will include epidemiologic, pathologic, prognostic as well as treatment response information. Particular attention will be given to study of patients whose primary cancers were assayed for receptor to determine relationship of receptor type (sedimentation coefficient) to disease-free interval, the receptor status and type of subsequent metastatic lesions, response to endocrine or chemotherapy, as well as survival.